In this study, we identified racial differences in the reported rate of TB infection in participants enrolled in the CARDIA study, an ongoing epidemiologic study of coronary artery risk development in young black and white adults. The CARDIA study collects individual-level data on a variety of socioeconomic indicators, including level of education, housing status, household size, and income level. In our analyses, the increased risk of TB infection in black participants persisted after adjusting for these socioeconomic indicators. The increased risk for TB infection in black participants also persisted after adjusting for other known risk factors for TB such as HIV infection, diabetes, renal disease, hematologic cancers, intravenous drug use, and incarceration, with black participants having a 2-fold increased odds of self-reported TB infection compared with white participants (P
< .001). Our findings suggest that factors other than comorbid conditions and socioeconomic status may contribute to the racial disparity seen in TB rates between blacks and whites in the US [1
]. Whether this disparity is due to unmeasured factors related to race as a social construct or due to biologic susceptibility factors is still subject to debate. An analysis of the influence of race/ethnicity on rates of active TB in the United States found that adjusting for 6 socioeconomic indicators accounted for approximately half the increased risk of TB previously ascribed to race/ethnicity among US-born blacks, Hispanics, and Native Americans [6
]. However, this study used ecologic-level data for socioeconomic indicators, specifically US Census data and zip code–specific demographic substratum values, whereas our study used individual-level data. Taken together, the numerous publications that show a link between race and increased risk of TB in US-born populations raise the question of whether targeted testing and treatment for LTBI should be recommended by race. Whether such a strategy would be cost-effective and whether it would have the potential to address the persistent disparity seen in TB between blacks and whites in the United States deserves further study.
Our study has limitations. First, CARDIA was focused on cardiovascular disease and consequently did not pursue diagnostic testing to confirm self-reports of HIV and TB. To address this, we limited our analysis to participants who provided consistent responses to the TB questions. Second, we could not clearly distinguish between patients with LTBI and those who may have had active TB. Consequently, we cannot comment on susceptibility to infection versus progression to disease. Third, although guidelines do not list race/ethnicity as indications for LTBI testing [14
], it is possible that there was differential testing for TB based on race, as has been reported for other primary care procedures [15
]. However, the increased risk for LTBI in non-Hispanic blacks reported in an analysis of National Health and Nutrition Examination Survey data on 7386 participants with tuberculin skin test results suggests that the association between race and TB is not an artifact of increased testing [3
]. We attempted to address this issue by controlling for characteristics that disproportionately affect blacks in the United States and may be indications for LTBI testing, including incarceration history and housing status, and race retained its association with self-report of TB. Nonetheless, differential testing as well as residual confounding may still exist.
In summary, we have shown that within a prospective, ongoing epidemiologic study of coronary artery disease in young black and white adults in 4 US communities, black study participants were 2 times more likely to report a history of TB infection compared with white participants after adjusting for a variety of socioeconomic factors, HIV status, intravenous drug use, diabetes, renal disease, and other traditional risk factors for TB. Our study suggests that factors other than socioeconomic status also contribute to the racial disparity in tuberculosis noted in US-born blacks.